Abstract

Partial and integral thermodynamic functions of the mixing and evaporation of nickel–calcium melts are calculated from the values of calcium vapor pressure at 900–1300°C (1173–1573 K), determined using the boiling points approach (isothermal version), and those of nickel, found via numerical integration of the Gibbs–Duhem equation. It is established that the formation of alloys containing up to 65.5 mol % calcium (the rest is nickel) is exothermic, while at higher Ca content the process is endothermic. The excess entropy of mixing is negative up to a Ca content of ∼64 mol %, testifying to a certain ordering in the melts due to the existence of associates. Using data on the pressure of a saturated vapor of calcium and nickel, the state diagram is supplemented by the fields of the coexistence of melts and vapor at atmospheric pressure and in vacuums of 1.33 and 0.7 kPa. The location of the boundaries of the fields of vapor–liquid equilibrium confirms the possibility of separation of the Ni–Ca melts by distillation in a vacuum.

中文翻译：

---

熔体的热力学和镍钙系统的状态图

摘要

镍钙熔体的混合和蒸发的部分和整体热力学函数是根据沸点法（等温版本）确定的，在900–1300°C（1173-1573 K）下的钙蒸汽压值计算得出的。镍，是通过吉布斯-杜海姆方程的数值积分发现的。可以确定的是，含钙量高达65.5 mol％（其余为镍）的合金是放热的，而在Ca含量较高时，该过程是吸热的。直到Ca含量约为64 mol％，混合的过量熵为负，这证明了由于缔合体的存在，熔体中的某种顺序。使用有关钙和镍饱和蒸气压力的数据，状态图由大气压下以及真空度为1.33和0.7 kPa的熔体和蒸气共存的场补充。气液平衡场边界的位置确定了通过真空蒸馏分离Ni-Ca熔体的可能性。